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FET could improve pregnancy rates in IVF; however, how much time is needed for the endometrium to return to optimal receptivity after ovarian stimulation is not known.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Electronic search in MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials to identify studies providing data on the influence of the interval between embryo freezing (or OPU) and FET in FET cycles published between January 1, 2007, and February 1, 2020.<\/jats:p><\/jats:sec><jats:sec><jats:title>Main findings<\/jats:title><jats:p>Data analyzed indicated that in the immediate FET cycles, there was a trend to an increased biochemical pregnancy rate (RR\u00a0=\u00a01.08; CI\u00a0=\u00a01.00\u20101.18), whereas the clinical pregnancy rate was somewhat higher, but without reaching statistical significance (RR\u00a0=\u00a01.07; CI\u00a0=\u00a00.99\u20101.15). The live birth rate was similar in the two groups (RR\u00a0=\u00a01.05; CI\u00a0=\u00a00.95\u20101.15), as was the implantation rate (RR\u00a0=\u00a00.98; CI\u00a0=\u00a00.83\u20101.16). Stratifying by embryo stage or FET type (freeze\u2010all or FET after failed fresh transfer) showed no differences.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Systematically delaying FET does not offer benefits to IVF outcomes. 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